[xwiki-users] Failed to migrate database from release 3.4 to 4.1.2

Hi, I try to install the release 4.1.2 on 3.4. During the database migration, there is this error message : 2012/06/27 13:26:54 [http://172.24.1.135:8080/xem/bin/view/Main/] INFO c.x.x.s.m.h.R40000XWIKI6990DataMigration - [R40000XWIKI6990] - Converting 12568 document statistics IDs in 1 tables and 0 collection tables... 2012/06/27 13:26:58 [http://172.24.1.135:8080/xem/bin/view/Main/] WARN o.h.util.JDBCExceptionReporter - SQL Error: 1062, SQLState: 23000 2012/06/27 13:26:58 [http://172.24.1.135:8080/xem/bin/view/Main/] ERROR o.h.util.JDBCExceptionReporter - Duplicate entry '-5487128615380216001' for key 1 2012/06/27 13:26:58 [http://172.24.1.135:8080/xem/bin/view/Main/] INFO c.x.x.s.m.h.HibernateDataMigrationManager - Failed to migrate database [xwiki]... com.xpn.xwiki.store.migration.DataMigrationException: Data migration R40000XWIKI6990 failed Somebody could help me about this message ? Even in debug mode, I don't have any information about this duplicate entry (which table ? which column ?) Thank you for any help. Nicolas